CVE-2026-66307: Skype for Business and Lync Denial of Service Vulnerability

Overview

Severity

High (CVSS 7.5)

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Category

Denial of Service

Exploit Status

Not Exploited

Exploitation Likelihood

Less Likely

Patch Tuesday

2026-Sep

Released

2026-09-08

Description

Integer underflow (wrap or wraparound) in Skype for Business allows an unauthorized attacker to deny service over a network.

Affected Products (3)

Microsoft Office

• Skype for Business Server 2015 CU13
• Skype for Business Server Subscription Edition CU1
• Skype for Business Server 2019 CU8

Security Updates (1)

• 5123287

Acknowledgments

Manish kumar, Pranjal Varshney

Revision History

• 2026-09-08: Information published.